//调用函数求三个数中最大值
#include<stdio.h>
int main(){
    int max();
    extern int A,B,C; //把外部变量A，B，C的作用域扩展到从此处开始
    printf("Please enter three integer numbers");
    scanf("%d %d %d",&A,&B,&C);
    printf("max is %d\n",max());
    return 0;
}

int A,B,C; //定义外部变量

int max(){
    int m;
    m=A>B?A:B;
    if(C>m)
        m=C;
    return (m);
}

